For watering stall and grazing animals, different sorts of automatic drinking bowls have come into use. In some, a valve is normally worked by the animal pushing against a release such as a lever or the like, as for example a lever bar or loop of metal placed within the bowl. However, such prior art bowls have shortcomings, especially for watering different sorts of animals from a single bowl. In fact, about 25 liters of water a minute are needed for watering each head of cattle so that the valve design has to be such that the valve is opened wide, and if the valve is to be opened by the force of the animal itself, a high degree of force is necessary. On the other hand, young stock will have trouble on using such valves and the natural drinking and swallowing will be hard if the animal has to keep working, or only working between gulps, some special valve system.
The same sort of problems are likely to arise in the case of automatic watering apparatus functioning without a bowl and simply in the form of a rubber disk fixed at the end of a water pipe and kept pressed elastically, because of its own elastic properties, against a ring-like lip so that the disk may be moved by a push rod which has to be displaced by the animal itself, so that, when the rod is pushed or turned, the rubber disk is so moved out of position that the water may make its way out past the ring-like lip and the rod (see German Offenlegungsschrift No. 2,306,280).
For decreasing the amount of force necessary for working a bowl valve, a suggestion has been in German Offenlegungsschrift No. 2,626,612 to make use of a watering valve with a cylindrical housing, which is joined with one end of the water pipe and which has a driving button sticking out of its upwardly running top end, the button being responsible for operating a small pilot plug of a plug-valve against the normal water pressure in a hollow valve cone, the plug being so freed of pressure so that, by pushing on the driving button further, it may be moved into the opened position.
Using such a system, it is true that the force needed right at the start for working the valve may be greatly decreased, but the degree to which the valve may be opened, that is to say the cross-section which is unblocked, is still limited so that, in the case of watering systems for grazing animals in which a water head of frequently only 200 to 300 millimeters is available, very large valve sizes have to be used so that, because such valves are made of metal, the price is high.